Improved truss-bridge



UNITED STATES PATENTOFFIGE.

Geenen r'. HERTHEL, Ja.,

IMPROVED TRUSS-BRIDGE.

Specification forming part of Letters Patent No. 86,227, dated January 26, lS69.

To all whom 'it'may concern:

Be it known that I, GEORGE P. HERTHEL, Jr., of ,the city of* St. Louis, in the county of St. Louis and State of Missouri, have made y certain new and useful Improvements in Truss- Bridges; and I do hereby declare that the following isa fulland clear description thereof,

reference being had to the accompanying drawings, and to the' letters of reference marked thereon.

It is well known that the braces of a trussbridge are subject to a maximum strain only when thetransient load carried by the 'brid ge occupies a certain position relatively to said braces; but, as the braces must be constructed of a strength of material to resist the maximum strain, it is apparent that the braces 'during their action, under any but the position of load causing amaximum strain, have a surplus of strength. The nature of this invention is now to employ said surplus of strength to strengthen certain 4other parts of the truss, and thus to permit and make an economy of material in such other parts. These are usually the upper and sometimes the lower chords of the truss.

It will hereafter be' seen that in the applica tion of the braces for trussing upper or lower chords a series of what may be called secondary trusses is formed; and this gives rise to certain new features of detail construction,

'which thus are resultante from the nature of this invention, as aforesaid.

It is well known that it is usual to construct trusses of bridges and similar structures with certain parts adjustable, thus enabling an operator to adjust such parts to any inequalities of construction or action, and when such structures, after use, become permanently deflected below their original outline, or sagged, they are drawn up, or cambered, at the points of 'adjustability. It seems apparent that in the repeated adjustments thus made, the parts so drawn up or readjusted should be subjected to greater strain than originally intended, and thus a weakening of the structure may arise. In order to counteract such effects, and generally to form, after adjustment, a stronger and.- safer structure, the nature of this invention is in such an arrangement for readjusting the vertical members, posts, or struts of a truss that thereby 0F s'lQLoUis, MIssoUni.

the truss height between the centers of chords will be increased, thereby increasing the resistance of the truss to strains, and counter, balancing, in whole or part, the undue strain on any individual member of the truss caused in the process of adjustment. Y

To enable those, skilled herein to make and use my said improvements, I will now more fully describe the same, referring to Figure 1 as a general side elevation; to Fi". 2 as an end elevation; to Fig. 3 as an enlarged detail elevation; to Figs. 4 and 5 as detail section and elevation, respectively showing one form of connecting posts with the upper chords; and to Figs. 6 and 7 as detail section and elevation, showing a second form of connecting posts and upper chords.

The features heretofore indicated as peculiarly in the nature of this invention are in no wise limited to the special details now to be described, and the forms as indicated'in the figures are intended as representative of one form of the application of the said features.

I construct the upper chord of the chordpieces A, which are usually cast-iron pipes, abutting against kin g-bolts a.

The posts or struts B abut also against said kin g-bolts, and the braces C attach thereto by any usual form of joint.

The queen-bolts d pass between the bands AD of the lower chord, generally as indicated in Figs. 1, 2, and 3.

To said queen-bolts the braces G again couneet, and the struts B abut thereagaiust, similarly as with the king-bolt a.

The braces cross at the point o, and a tiebolt, c, passes through the same, thus connecting both main and counter braces.

Upon said cross-bolt c1, I arrange a sleeve, c2, which forms the abutmentfor the secondary post or strut b, and at the top this post connects, by a kin g-bolt, a', with the upper chord-piece, A, similarly as at the main-post joint.

'By this construction the length of the upper chord-pieces between main posts B has been halved, and thus a great length of panel may be used, and the advantages following from a moderate length of chord-pieces A still retained.

Moreover, as every kingbolt is usually the pintfor the arrangement of door-beams E, it will be seen that the number of supports for `f the roadway of the bridge is largely increased.

The Hoor-beams E, I arrange upon the saddle-plate e, which sits upon ,the bolts a. a' as indicated .in the detail figures. y It is plain that the effect of a load upon the strut b, and herefrom upon the braces of any panel, is exercised only when that panel is subjected to load; and as it is true that the braces of this panel are not then subjected to a maximum strain, it is apparent that the surplus strength ofthe braces at the time the panel acts under a load is fairly economized.

Similarly, in case theload rests more immediatelyupon thev lower chord, I arrange a postbolt, F, passing A from the king-bolt a to a main queen-bolts d, as indicated in Figs. 1 and 3. l

New, as the upper chord of a truss is subject to compression by the action of loadson the truss,it may be necessary to prevent the bolta' and its connecting chord-pieces from rising. This I accomplish either by a postbolt, F, extending fully to the lower chord, or extending only 'to thelower surface of the sleeye c of the cross-bolt c1.

vIn the latter case the upward strain upon v such bolt F acts upon the lower parts oi" the braces, and therefrom upon the lower chords, D, and`1nain posts B, and is further thence distributed.

Thebolt F may be -continued vup to Vhold down the door-beams E, as in Figs. 3 and 5. A'second method of preventing the upper strap-bolts f, which pass about a flange of the posts b, and either around the bolt a or go up to secure the'loor-beams E, as in Figs. 6 and 7. In this case a similar strap, f', holds the lower end of the post b'to the sleeve c2.

In order to adjust or readjust the parts here queen-bolt, d', placed in the lowerchord ,and similarly joined tol the latter, as were the` chord from buckling up at the joint a' is by the described, I arrange, at the top or bottom of the main posts B or secondary posts b, a series of key-plates, g. These are of horizontal surfacewhere they connect with the post, but are inclined on their upper surfaces, Where a they rest against the connecting king or Iqueen boltor sleeve. A set-Of'snlall bolts g, is used to draw said key-plates together and secure them. If,`now, the nut of said bol ts g is drawn up, the key-plates will be drawn together, and thus the king and queen bolts forced apart, the said operation being equivalent to length- "ening the posts B or b,`andthus increasing the truss height. But as hereby the strength of the truss is materially increased, if the load upon thetruss be constant, the received strain oneach part will bev correspondingly .decreased, owing to said' increased height ofr truss, and thus any overstrain caused in adjusting any part will be in a degree counterbalanced.

'Having thus fully described mysaid invention, what I claim is- 1. Connecting the main and counter braces with a secondary post, b, and with an intermediate point ofthe upper chord, to increase the number'of points of support for the roadway, and shortenthe lengths of the chordpieces A, substantially as set forth.

2. The arrangement of the rod F, connecting the upper and lower chords at the point of .juncture of the *mainl and counter braces andthe secondary post-b,substantially as set forth.

3. The arrangement of the straps j f' or'the rod F with the posts b and the bolt a4 or floor-beams E, substantially as set forth.

4. rlhe wedgeplates g, constructed and arranged, in connection withV the post b or B,

' substantially as set forth.

o GEO, r. HERTHEL, JR. Witnessesz i J. W. HERTHEL,

' ROBERT BURNS. 

